reserve c, c1, c2, d, d1, d2, e, y for Real,
  k, n, m, N, n1, N0, N1, N2, N3, M for Element of NAT,
  x for set;

theorem
  for k,n being Nat st k <= n holds n choose k >= ((n+1) choose k) / (n+1)
    by Lm43;
